This invention relates to computerized axial tomographic (CAT) analysis and, more particularly, to the determination of the spatial distribution of three phases, i.e., water, oil and gas in a sample, such as a core sample from a borehole during fluid flow through the core. The saturation of the three phases in the sample can be measured dynamically during a laboratory displacement process.
The determination of three-phase saturations by computerized axial tomography (hereinafter referred to as "CAT") is based on the fact that X-ray attenuation depends both on the density and the chemical composition of a material. For mean energies above about 100 keV X-rays interact with matter predominantly by Compton scattering which is dependent on electron density. For X-ray energies below a mean energy of 100 keV, photoelctric absorption becomes important; this type of interaction is strongly dependent on atomic number.
The prior art has suggested the use of X-rays for measuring oil saturation in rock cores. These methods have all related to two-phase flow and used a single X-ray energy and an average measurement over a cross section of the core. The resulting displays were one dimensional and do not provide information relating to discrete variation in the flow pattern across the section. The prior art has also suggested use of CAT to obtain a two dimensional plot of fluid movement through the core. The prior use of CAT has been two-phase single energy X-ray scanning of the core under atmospheric temperature and pressure.